检查excel文件是否被其他用户打开
问题描述:
我有一个excel文件放在服务器上。检查excel文件是否被其他用户打开
我正在使用VB.NET编写的应用程序以只读模式打开文件。
用户1以只读模式打开文件。 用户2如何检测该文件是否处于打开状态?
感谢, 的
答
您需要测试文件只读,因为如果文件为ReadOnly状态,ReadWrite将失败。 下面是一些方法。不知道除了Randy Birch的最后一张之外,我从哪里得到了他们。 速度测试有利于FileIsOpen3和FileIsOpen4。
Function FileIsOpen1(ByVal pathfile As String) As Boolean
Dim ff As Integer
If System.IO.File.Exists(pathfile) Then
Try
ff = FreeFile()
Microsoft.VisualBasic.FileOpen(ff, pathfile, OpenMode.Binary, OpenAccess.Read, OpenShare.LockReadWrite)
Return False
Catch
Return True
Finally
FileClose(ff)
End Try
Return True
End If
End Function
Function FileIsOpen2(ByVal pathfile As String) As Boolean
Dim stream As FileStream = Nothing
Dim fi As FileInfo = Nothing
If System.IO.File.Exists(pathfile) Then
Try
fi = New System.IO.FileInfo(pathfile)
stream = fi.Open(FileMode.Open, FileAccess.Read, FileShare.None)
Return True
Catch generatedExceptionName As IOException
Return False
Finally
If stream IsNot Nothing Then
stream.Close()
End If
fi = Nothing
End Try
Return True
End If
End Function
Private Function FileIsOpen3(ByVal pathfile As String) As Boolean
Try
Dim fs As IO.FileStream = IO.File.Open(pathfile, IO.FileMode.Open, IO.FileAccess.Read, IO.FileShare.None)
fs.Close()
fs.Dispose()
fs = Nothing
Return False
Catch ex As IO.IOException ' File open
Return True
Catch ex As Exception ' Unknown error
Return True
End Try
End Function
Private Declare Function CreateFile Lib "kernel32" _
Alias "CreateFileA" _
(ByVal lpFileName As String, _
ByVal dwDesiredAccess As Long, _
ByVal dwShareMode As Long, _
ByVal lpSecurityAttributes As Long, _
ByVal dwCreationDisposition As Long, _
ByVal dwFlagsAndAttributes As Long, _
ByVal hTemplateFile As Long) As Long
Private Declare Function CloseHandle Lib "kernel32" _
(ByVal hFile As Long) As Long
' Method
Shared Function FileIsOpen4(ByVal pathfile As String) As Boolean
' Is File In Use ©1996-2009 Randy Birch
' http://vbnet.mvps.org/index.html?code/fileapi/createfile_inuse.htm
Const GENERIC_READ As Long = &H80000000
Const INVALID_HANDLE_VALUE As Long = -1
Const OPEN_EXISTING As Long = 3
Const FILE_ATTRIBUTE_NORMAL As Long = &H80
Dim hFile As Long
If System.IO.File.Exists(pathfile) Then
Try
' note that FILE_ATTRIBUTE_NORMAL (&H80) has a different value than VB's constant vbNormal (0)!
hFile = CreateFile(pathfile, GENERIC_READ, 0, 0, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, 0&)
' this will evaluate to either -1 (File in use) or 0 (File free)
Return hFile = INVALID_HANDLE_VALUE
Catch ex As Exception
MessageBox.Show(ex.ToString)
Finally
CloseHandle(hFile)
End Try
Else
Return True
End If
End Function
答
第二用户可以尝试打开该文件在读写模式下知道如果正在使用的文件。
听起来并不理想,但它是真实的。即使你有一些方法来检测锁是否有可能在你的锁定检查和实际打开文件之间有人可以打开文件,所以最好的办法就是尝试打开文件并捕获异常(如果有的话)。 – 2010-03-31 13:13:47